1. Field of the Invention
The present invention relates to an amplifier and in particular to an amplifier comprising one or more switches controlled by a hysteresis block.
2. Discussion of the Related Art
Switching amplifiers, such as class D audio amplifiers, are amplifiers that generate an output voltage by switching an output node between a supply voltage and a ground voltage. The duration of the pulses during which the output node is coupled to the supply voltage determines the output voltage level. This is controlled by a feedback loop that drives the switches.
It has been proposed to provide a hysteresis stage in the feedback loop for controlling the switches.
It is often an aim when designing such amplifiers to minimize noise and distortion at the output node. However, known designs that use hysteresis stages tend to have poor power supply rejection ratio (PSRR) meaning the effect of ripples in the power supply is relatively high on the output voltage. There is thus a need for a switching amplifier with a good PSRR.